Method for introducing reeled tubing into oil and gas wells

ABSTRACT

A method for introducing reeled tubing into oil and gas wells, in which a relatively stiff pipe segment is connected to the leading end of the reeled tubing before the reeled tubing is introduced into the well. The reeled tubing, with the pipe segment attached to its leading end, is unwound from its reel and the pipe segment reduces damage to the wall of the well and jamming of the reeled tubing in the well as the tubing passes through the well.

BACKGROUND OF THE INVENTION

The present invention relates to a method for introducing reeled tubinginto oil and gas earth wells and, more particularly, to such a methodwhich reduces damage to the wells and prevents jamming of the reeledtubing in the wells.

In the operation of subterranean oil and gas earth wells, relativelysmall-diameter, thin-walled, continuous-length reeled, or coiled, tubingis now being used in certain applications in place of wireline or thelike, since reeled tubing has several advantages. For example, reeledtubing does not rely on gravity for setting and retrieving the operatingtools can thus can traverse highly deviated, or horizontal, earth wells.Also, reeled tubing can be more rapidly inserted into the well and canbe more easily passed through downhole equipment. Also, fluids such aswater, foam, paraffin, corrosion inhibitors, spotting acid, cement, andthe like, can be conveyed by the reeled tubing to the well forperforming various functions including washing and cleaning. Further,when used with operating tools the reeled tubing can be used to conveyfluids to the operating tool to hydraulically actuate the tool.

Reeled tubing is usually made from soft-sheet steel which is rolled andinduction welded along its length before being spooled onto a deploymentreel. The tubing is then heat-treated on the reel to stress-relieve thetubing wall and the seam weld. Several sections of tubing are thenbutt-welded together to achieve lengths of up to several thousand feetfor reaching the treatment zone in the well.

In the deployment of reeled tubing, the tubing is unreeled from thereel, typically at or near ground level and usually passed over agoose-neck and into an injector head located axially above the wellheadand the wellbore. The injector head typically comprises a dualchain-driven mechanism which drives the reeled tubing into, and pullsthe tubing from, the well.

During this process, torsional forces are applied to the tubing as it iswound on, and unwound from the reel and passed upwardly to thegoose-neck. Also, the tubing is plastically deformed as it is drawn fromthe reel and passed over the goose-neck and into the injector head.Further, tensil forces are applied to the tubing due to the pullingforce of the injector head drive mechanism and a braking or rewind forceapplied at the reel. Also, the tubing leaving the injector head andgoing into the well is disposed in the well in a long helix which causesthe tubing and especially the end thereof, to engage the walls of thewell which often causes damage to casing well tubing, or the like,disposed in the well.

This problem is compounded since, once the zone of treatment has beenreached by the end of the reeled tubing, typical operations may requirecycling of the reeled tubing upwardly and downwardly over an interval upof hundreds of feet causing bending and unbending of portions of thereeled tubing located at or near the surface as the tubing passes andre-passes the injector head, the goose-neck and the reel. Finally, inremoving the reeled tubing from the well, the entire length of thedeployed tubing is again subjected to all of the above forces andplastic bending in reverse order as it is wound back onto its reel,further increasing the changes of damage to the casing and/or welltubing. Also as a result of all of the foregoing, the end portion of thereeled tends to lodge, or jam, in the well, especially in wells having ahorizontal portion.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodfor introducing reeled tubing into an oil and gas earth well.

It is a further object of the present invention to provide a method ofthe above type which reduces damage to the casing or well tubing in thewell.

It is a further object of the present invention to provide a method ofthe above type which reduces the tendency of the end portion of thereeled tubing to jam in the well.

Toward the fulfillment of these and other objects, according to themethod of the present invention, a relatively stiff pipe segment isconnected to the leading end of the reeled tubing before the reeledtubing is introduced into the well. The reeled tubing, with the pipesegment attached to its leading end, is unwound from its reel and thepipe segment functions to reduce damage to the casing or well tubing inthe well and jamming of the reeled tubing in the well.

DESCRIPTION OF THE DRAWING

The above brief description, as well as further objects, features andadvantages of the present invention will be more fully appreciated byreference to the following detailed description of the presentlypreferred but nonetheless illustrative embodiments in accordance withthe present invention when taken in conjunction with the accompanyingdrawing which is a schematic view, partially in elevation and section,and partially broken away, of a deviated oil and gas earth well, showingreeled tubing after it has been introduced into the well according tothe method of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawing, the reference numeral 10 refers to a deviatedoil and gas earth well extending below ground and having a generallyvertical section 10a and a generally horizontal section 10b. An outercasing 12, of a cementaceous material is formed against the wall of thewell and extends from ground surface to approximately the lower end ofthe vertical section 10a of the well. An inner casing, or tubing 14,extends within the casing 12 in the vertical well section 10a.

A section of reeled tubing 20 is stored on a reel 22 above ground and isinjected into the inner casing 14 by an injector 24. The reeled tubing20 is formed in the manner discussed above by a plurality of sectionsconnected at their respective ends which, according to a preferredembodiment, are thirty feet in length, and the wall thickness of thereeled tubing is such that it is flexible enough to be wound on the reel22.

It is understood that a goose-neck (not shown) can be provided on theinjector 24 and a manifold (not shown) can be provided which includesthe necessary pumps, valves, and fluid reservoirs to discharge a fluidinto and through the reeled tubing 20. It is also understood that awellhead valve (not shown) is used to control vertical access to, andfluid communication with, the upper portion of the inner casing 14, andblowout preventers, or the like (not shown), can be installed to blockfluid flow during emergency conditions. Since these components areconventional they will not be described in any further detail.

The reeled tubing 20 is shown extending through the vertical section 10aof the well 10, through an angled or curved section and into thehorizontal section 10b, and is installed according to the method of thepresent invention. More particularly, before any of the reeled tubing 20is introduced into the casing 14, a rigid section of pipe 30 isconnected to the free, or distal, end of the reeled tubing. Theconnection is made in any conventional manner, such as by formingcooperating internal and external threads on the corresponding endportions of the reeled tubing 20 and the pipe 30. The length of the pipe30 is less than that of each of the sections forming the reeled tubingand according to a preferred embodiment is six feet. The diameter of thepipe 30 is substantially the same, or slightly greater (as shown) thanthe diameter of the reeled tubing 20 and the thickness of the pipe, orthe material forming the pipe, is such that it is stiffer, or morerigid, than the reeled tubing.

The pipe 30, with the end of the reeled tubing 20 connected to itstrailing end, is introduced into the upper portion of the casing 14, andthe reeled tubing is played out from the reel 22 to force the pipe 30and the tubing into and through the casing 14. The pipe 30 and thereeled tubing 20 pass through the casing 14 in the vertical section 10aof the well and then into the uncased, substantially horizontal wellsection 10b before taking the position shown in the drawing. During theintroduction of the pipe 30 and the reeled tubing 20 into the well 10,the relatively short and rigid pipe 30 increases the structuralintegrity of the tubing 20 and "guides" the tubing through the wellwhile minimizing the tendency of the end portion of the reeled tubing toengage the wall of the casing 14, and/or become stuck or jammed whichotherwise would occur due to the helical shape that the reeled tubingtakes as it traverses the well, and due to the plastic bending of, andthe forces on, the tubing as discussed above.

According to a preferred embodiment, the pipe 30 can be in the form of a"pup joint" manufactured, for example, by the Tube-Alloy Corporation ofHouston, Tex. which is available in lengths from two feet to ten feet.In addition to being shorter in length than the individual sections ofthe reeled tubing 20, the pipe section 30 is more rigid than the tubing,which rigidity can be achieved by manufacturing the pipe section of athicker wall and/or of a more rigid material.

Washing or cleaning fluid can be introduced from the manifold describedabove into the reeled tubing 20 during its introduction into the well 10and/or after it attains the position shown in the drawing. In eithercase the fluid would pass through the pipe 30 and discharge from itsfree end to perform the washing or cleaning operation.

It is understood that an operating tool, such as shown by the referencenumber 32, can be attached to the free end of the pipe 30 withoutdeparting from the scope of the invention, as long as the tool does notinterfere with the function of the pipe 30, as described above.

It should be emphasized that variations in some of the parameters setforth above can be made without departing from the scope of theinvention. For example, the diameter and length of the pipe 30 can varyfrom the examples described above.

Other modifications, changes and substitutions are intended in theforegoing disclosure and in some instances some features of theinvention will be employed without a corresponding use of otherfeatures. Accordingly, it is appropriate that the appended claims beconstrued broadly and in a manner consistent with the scope of theinvention.

What is claimed is:
 1. A method of installing relatively flexible tubingwound on a reel into an earth well, comprising the steps of attaching arelatively stiff pipe onto the leading end of said tubing, theninserting said pipe and said attached tubing into said earth well, andthen unwinding said tubing from said reel to force said pipe and saidtubing through said well, said pipe reducing the tendency of said tubingto engage the well of said well and/or become jammed in said well. 2.The method of claim 1 further comprising the step of introducing fluidinto said tubing for discharge from said pipe into said well.
 3. Themethod of claim 1 wherein said tubing is formed by a plurality oftubular sections connected together at their respective ends, andwherein the length of said pipe is less than the length of each of saidtubular sections.
 4. The method of claim 1 wherein said pipe is in theform of a pup joint.
 5. The method of claim 1 further comprising thestep of attaching a tool to said pipe after said first step of attachingand before said step of inserting.
 6. The method of claim 1 wherein saidearth well has a generally vertical-extending section and a generallyhorizontal-extending section.
 7. A method of operating as earth well,including the steps of winding relatively flexible, continuous lengthtubing on a reel, then inserting said tubing into said earth well, andthen unwinding said tubing from said reel to force said tubing throughsaid well, said steps of winding and unwinding creating torsional forcesand plastic bending that forces the tubing against the wall of the wellwherein the improvement comprises the step of attaching a relativelystiff pipe onto the leading end of said tubing before said step ofinserting to guide said tubing through said well to reduce the effect ofsaid forces and said bending.
 8. The method of claim 7 furthercomprising the step of introducing fluid into said tubing for dischargefrom said pipe into said well.
 9. The method of claim 7 wherein saidtubing is formed by a plurality of tubular sections connected togetherat their respective ends, and wherein the length of said pipe is lessthan the length of each of said tubular sections.
 10. The method ofclaim 7 wherein said pipe is in the form of a pup joint.
 11. The methodof claim 7 further comprising the step of attaching a tool to said pipeafter said first step of attaching and before said step of inserting.12. The method of claim 7 wherein said earth well has a generallyvertical-extending section and a generally horizontal-extending section.